Strip wiper device, strip wiping method, rolling mill and rolling method

ABSTRACT

To improve the productivity of the cold rolling facility by providing the cold rolling facility with a strip wiper free of dust and foreign matters suitable for high-speed rolling. The wiping ability was greatly improved by floating and supporting the wiper roll by the static pressure bearing of air of two-pocket type, and by variably adjusting the load range of the floating force in response to the plate width. At high-speed rolling exceeding 700 m/min which was incapable with the conventional roll wiper or tube wiper, the productivity of the cold rolling facility and the surface quality of the strip were greatly improved by applying to the cold rolling facility the wiping device whose wiping ability is equal to or better than the tube wiper at low speeds, and its effect is very large.

This application is a 35 USC 371 of PCT/JP99/01677, filed Mar. 31, 1999.

BACKGROUND OF THE INVENTION

The present invention relates to a strip wiper, strip wiping method,rolling facility, and rolling method.

In rolling operation, a rolling lubricant is supplied to the entrance ofa rolling mill so as to reduce friction between the strip (rolledmaterial) and the rolling work roll and to cool the work roll.Particularly, in cold rolling operation with a 20-high Sendzimir rollingmill having work rolls of extremely small diameter or a 6-high rollingmill having work rolls of small diameter, a lubricant is supplied alsoto the exit of the rolling mill so as to increase the cooling capacityof the work rolls.

Moreover, in the rolling of shadow mask materials by rolling mills, dullrolling with dull rolls is carried out in the final pass of rollingprocess so as to roughen the surface of the rolled material. In dullrolling like this, the surface of the rolled material is soiled withdull powder (powder fall off from the dull roll) and hence a rollinglubricant is supplied to the exit of the rolling mill to wash out thedull powder.

The rolling mills supplied with a lubricant as mentioned above yieldrolled strips carrying a large amount of lubricant on their surface.When a strip is wound into a coil, with its surface carrying a largeamount of rolling lubricant supplied at the entrance of the roll mill,particularly at the exit of the roll mill, the wound coil becomes a“telescope”, with each layer slipping sideward due to rolling lubricantpresent between layers. The telescoped coil leads to meandering andirregular forms, inhibiting stable rolling operation.

Also, in the case where there exists bridle rolls (to add tension to thestrip) at the exit of the rolling mill, the rolling lubricant extremelydecreases the coefficient of friction between the bridle rolls and thestrip, disabling stable operation (as in the case mentioned above) dueto insufficient tension.

It is the strip wiper that removes the rolling lubricant from the stripsurface. The strip wiper is available in different types, such as tubewiper, roll wiper, and air-jet wiper.

A tube wiper is highly capable of wiping but its tube is short in lifewhen foreign matter (such as dust) enters it. This is significantparticularly in the case of high-speed operation. A tube wiper for dullrolling has the disadvantage of impairing the surface quality of therolled material due to tube clogging with dull powder.

As a substitute for this, a roll wiper has been proposed in JapanesePatent Publication No. 60403/1990. It is designed to improve the wipingcapacity by pressing the staggered split back-up rolls individually withsprings, thereby distributing the pressing force toward the tripuniformly in the widthwise direction. The disadvantage of this system isthat the wiper roll is bent by the supporting force of the back-up rollextending outside the strip width, resulting in a poor shape with anelongated end, if the pressing force is strong. This wiper roll,therefore, is poor in wiping ability due to limited pressing force. Atthe time of high-speed operation, the wiper roll, which is not driven,does not rotate due to hydroplaning which results from the fact that therolling lubricant on the roll surface forms an oil film between the rolland the strip. The result is incomplete wiping, or the non-rotating rollscratches the strip surface. In addition, this roll wiper is liable tostop because of many back-up rolls and its comparatively high bearingseal resistance.

In order to address this problem, there has been proposed a roll wiper(having a wiper roll supported by an air bearing) in Japanese Patent No.2523725. It has a small diameter for good wiping performance because itis supported uniformly on its surface by an air bearing. In addition,the roll wiper of air bearing type has its roll floated and supported byhigh-pressure air, so that it has a very low rolling friction. Itremains turning at speeds as high as 700 m/min, and hence it is suitablefor high-speed rolling.

Unfortunately, the roll wiper of air beating type has never been put topractical use because of its low wiping performance which results fromthe fact that the air bearing is lower in its load capacity than thestatic bearing of hydraulic type. (It is to be noted that the airpressure for the air bearing is usually lower than 5 kgf/cm², whereasthe hydraulic pressure is as high as 100 kgf/cm².) Another problem isthat the air bearing of one-pocket type is low in rigidity in thehorizontal direction and hence the roll comes into contact with thebearing when it receives even a slight horizontal force. This preventsnormal operation. The roll rotating at high speeds affects the air flowin the beating (making the air flow asymmetric in the bearing), reducingfurther the horizontal rigidity to allow the roll to come into contactwith the bearing.

For the reasons mentioned above, it is desirable to propose a high-speedroll wiper capable of better wiping than the conventional tube wiper, byincreasing the load capacity of the air bearing and preventing theexcessive pressure at edges.

It is an object of the present invention to provide a strip wiper devicehighly capable of removing liquid from the strip surface, a method forstrip wiping, a rolling facility, and a rolling method.

SUMMARY OF THE INVENTION

The present invention is directed to a strip wiper device to removeliquid from the strip surface which comprises a wiper roll to removeliquid from the strip surface and a fluid bearing to support the wiperroll, with the fluid bearing having at least two fluid passages in thecircumferential direction of the roll.

The present invention is directed to a strip wiper device to removeliquid from the strip surface which comprises a first strip wiper and asecond strip wiper which are arranged sequentially in the direction ofstrip advance, the second strip wiper being made up of a wiper roll anda fluid bearing to support the wiper roll, with the fluid bearing havingat least two fluid passages in the circumferential direction of theroll.

The present invention is directed also to a strip wiper device to removeliquid from the strip surface which comprises a first strip wiper and asecond strip wiper which are arranged sequentially in the direction ofstrip advance, the second strip wiper being made up of a wiper roll anda fluid bearing to support the wiper roll, with the fluid bearing havingat least two fluid passages in the circumferential direction of theroll.

The present invention is directed also to a strip wiper device to removeliquid from the strip surface in cold rolling which comprises a firststrip wiper for rough wiping and a second strip wiper for finishingwhich are arranged sequentially in the direction of strip advance, thesecond strip wiper being made up of a wiper roll and a fluid bearing tosupport the wiper roll by pneumatic pressure, with the fluid bearinghaving at least two fluid passages (for pneumatic pressure to the wiperroll) in the circumferential direction of the roll, such that the wiperroll is supported by pneumatic pressure in two directions from the twofluid passages.

The present invention is directed also to a strip wiper device to removeliquid from the strip surface which comprises a first strip wiper and asecond strip wiper which are arranged sequentially in the direction ofstrip advance, the first and second strip wipers each being made up of awiper roll and a fluid bearing to support the wiper roll, with the fluidbearing having at least two fluid passages in the circumferentialdirection of the roll.

The present invention is directed also to a strip wiper device to removeliquid from the strip surface which comprises a first strip wiper and asecond strip wiper which are arranged sequentially in the direction ofstrip advance, the second strip wiper being made up of a wiper roll anda fluid bearing to support the wiper roll.

The present invention is directed also to a method of strip wiping toremove liquid from the strip surface which is characterized in thatwiper rolls supported by fluid bearings are arranged up and down, withthe fluid bearing having at least two fluid passages in thecircumferential direction of the roll, the fluid passage is suppliedwith a fluid so that the wiper roll is born by the fluid and is pressedagainst the strip.

The present invention is directed also to a method of strip wiping toremove liquid from the strip surface which is characterized in that awiper roll for rough wiping removes liquid from the strip surface andwiper rolls supported by fluid bearings are arranged up and down at thedownstream side, with the fluid bearing having at least two fluidpassages in the circumferential direction of the roll, the fluid passageis supplied with a fluid so that the wiper roll is born by the fluid andis pressed against the strip.

The present invention is directed also to a rolling facility whichcomprises a rolling mill and a strip wiper device to remove liquid fromthe strip surface at the exit of the rolling mill, said strip wiperdevice being made up of a wiper roll to remove liquid form the stripsurface and a fluid bearing to support the wiper roll, with the fluidbearing having at least two fluid passages in the circumferentialdirection of the roll.

The present invention is directed also to a rolling method to be appliedto a rolling facility made up of a rolling mill and a strip wiper deviceto remove liquid from the strip surface at the exit of the rolling mill,said method being characterized in that wiper rolls supported by fluidbearings are arranged over and under the strip, the fluid bearing has atleast two fluid passages in the circumferential direction of the rolland the passages are supplied with a fluid so that the wiper roll isborn by the fluid, and the wiper roll is pressed against the strip sothat liquid is removed from the strip surface while rolling is carriedout.

The present invention is directed also to a rolling method to be appliedto a rolling facility made up of a rolling mill and a strip wiper deviceto remove liquid from the strip surface at the exit of the rolling mill,said method being characterized in that a wiper roll for rough wipingremoves most liquid from the strip surface, wiper rolls supported byfluid bearings are arranged over and under the strip, the fluid bearinghas at least two fluid passages in the circumferential direction of theroll and the passages are supplied with a fluid so that the wiper rollis supported in two directions by pneumatic pressure, and the wiper rollis pressed against the strip so that liquid remaining unremoved by thewiper for rough wiping is removed from the strip surface while rollingis carried out.

The present invention is directed also to a strip wiper device whichcomprises a wiper roll to remove liquid from the strip surface and afluid bearing to support the wiper roll, said fluid bearing having atleast two fluid jet nozzles toward the wiper roll in the circumferentialdirection of the roll.

The present invention is directed also to a strip wiper device whichcomprises a wiper roll to remove liquid from the strip surface and afluid bearing to support the wiper roll, said fluid bearing having atleast one each fluid jet nozzle at the entrance and exit from the wiperroll axis center.

The present invention is directed also to a strip wiper device whichcomprises a wiper roll to remove liquid from the strip surface and afluid bearing to support the wiper roll, said fluid bearing having atleast two fluid jet nozzles toward the wiper roll in the circumferentialdirection of the roll, said jet nozzles being arranged such that theirjet direction is toward the wiper axis center.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of the 6-high rolling mill provided with a rollwiper of air bearing type according to the present invention.

FIG. 2 is a wiping device according to the present invention in whichrough wiping rolls are combined with roll wipers of air bearing type.

FIG. 3 is a sectional view (in the axial direction) of the finish wipershown in FIG. 2.

FIG. 4 is a diagram showing the structure of the air bearing.

FIG. 5 is a diagram showing the state of the load of the roll wiper ofair bearing type and the state of the roll deflection.

FIG. 6 is a diagram showing the state of wiping by the roll wiper.

FIG. 7 is another embodiment of the present invention in which rollwipers of air bearing type are arranged tandem.

FIG. 8 is a diagram showing the effect of the rough wiping roll.

FIG. 9 is another example of the present invention demonstrating a20-high Sendzimir mill cold rolling facility provided with the rollwiper of air bearing type.

FIG. 10 is a diagram showing the state of wiping of a rolled materialwith a plate crown.

FIG. 11 is a result of calculations of follow-up (to the plate crown) ofthe roll wiper of air bearing type.

FIG. 12 is a result of calculations of the critical roll radius at whichthe roll wiper of air bearing type begins to slip at the time ofacceleration and deceleration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The mode for carrying out the invention will be described in thefollowing.

In order to maximize the ability to wipe off rolling lubricant from therolled material (strip), it is necessary to optimize the parameter whichdetermines the wiping ability.

FIG. 6 is a partly enlarged sectional view in the case where the rollinglubricant 10 is removed from the surface of the strip 1 by using a roll.The thickness of the residual oil film remaining after wiping by theroll wiper shown in FIG. 6 is represented by the equation (1).

h 2=K·(R·ν·V)/P  (1)

where thickness of residual oil film: h2 (μm), proportionality constant: K (=6.1×10⁻⁶), wiper roll radius: R (mm), lubricant viscosity: ν(cSt), velocity: V (cm/min), and wiper roll pressing force: P (kgf/mm).

As understood from this equation (1), in order to increase the wipingability, it follows that the pressing force P should be increased byusing a roll having a small radius R. It is also understood thatreducing the lubricant viscosity ν is effective.

On the other hand, in one embedment of the present invention, thepressing force is maintained by the air bearing as shown in FIG. 4. Thispressing force P is represented by the following equation (2).

P=C·R·ps  (2)

Where, the proportionally constant C=0.25 in the case of one-pocket typein FIG. 4 (1), and the proportionally constant C=0.38 in the case oftwo-pocket type in FIG. 4 (2). And, the supply air pressure: ps(kgf/mm²).

The two-pocket type has 1.5 (=0.38/0.25) times larger load capacity ascompared with the one-pocket type. And, the two-pocket type is such thatthe rigidity in the horizontal direction (rolling direction) is almostas high as in the vertical direction, and contact between the wiper rollreceiving horizontal force and the static pressure bearing does notoccur easily and this is convenient. In other words, by making the fluidbearing of two-pocket type having the fluid passage of the fluid bearingor two fluid jet nozzles, the rigidity in the direction of rolledmaterial advance is superior and hence it is possible to support stablyand it is possible to obtain the superior wiping performance. Also, itis possible to increase the pressing force and to improve the wipingperformance, and it is possible to carry out wiping with high precision.

Incidentally, as shown in FIG. 4, in this example, an air chamber 23 bis installed in the vicinity of the air nozzle of the air supply hole 23a. By installing the air chamber 23 b, the stabler roll support becomespossible. And, by installing the air chamber 23 b such that it extendsin the circumferential direction of the roll as shown in FIG. 4, it ispossible to stabilize more the roll support in the radial direction ofthe roll.

Also, in the three-pocket type with an additional pocket at the centerof two-pockets or the type having more than four pockets, it isconsidered that there is no significant difference from the two-pockettype in both the vertical load capacity and horizontal rigidity.However, in the type with more than three pockets, the consumption ofair used increases. In other words, adding the vertical load capacityand the horizontal rigidity together and considering the amount ofconsumption of air, the two-pocket type is desirable. Here, thetwo-pocket type is one in which the fluid passage supporting for its oneroll has two in the roll circumferential direction, and it is desirablethat they are installed at the entrance and the exit respectively, withthe roll axis being the boarder. And, the jet nozzle (supply hole) ofits fluid is desirably one which has two in the roll circumferentialdirection, and it is desirable to install two jet nozzle at the entranceand the exit respectively in the roll circumferential direction, withthe roll axis center being the boarder. And, the jet direction of thefluid (the supply direction toward the roll) is desirably the directiontoward the roll axis center, and the stabilization of the roll supportcan be designed. Incidentally, it is desirable to install at lease oneeach jet nozzle at the upstream side and the downstream side from thevertical plane including the roll axis.

And, from the equations (1) and (2), the residual oil film thickness h2is represented by the equation (3) below.

h 2=K·(ν·V)/(C·ps)  (3)

From this equation (3), in order to increase the wiping ability, it isunderstood that increasing the supply air pressure ps is effective. And,it is understood that it is effective to make the type of air bearingtwo-pocket type and increase the proportionality constant C. And, thewiper roll radius R is independent of the residual oil film thicknessh2, but the follow-up to the plate crown is better when the roll radiusR is small, therefore, it is desirable that the roll radius R is small.

Here, we roughly calculate the air pressure necessary for actualoperation. At present, the wiping ability required of shadow mask rolledmaterial is as follows. In the case of velocity V: 500 m/min, lubricantviscosity ν: 5 cSt (equivalent to velocity V: 250 m/min, lubricantviscosity ν: 10 CSt), the required residual oil film thickness h2 is 0.7μm (corresponding to 630 mg/m²). And, from the equation (3), if therequired air pressure is calculated, it follows thatps=K·(ν·V)/(h2·C)=6.1×10⁻⁶×(5×500)/(0.38×0.7)=0.0053 (kgf/mm²)=5.73(kgf/cm²).

From this, it follows that it is desirable that the air pressure isclose to 6 kgf/cm², and higher than 5 kgf/cm² at the lowest. (Being5/5.73=0.87, the wiping ability of 87% of the above-mentioned operatingvalue, a difference of this degree is usually permissible.)

Then, we explain the adequate value of this roll radius. As one factorto determine this roll radius, the follow-up to the plate crown isconsidered. In this example, we paid our attention to this follow-up tothe plate crown. As shown in FIG. 10, a quadratic thickness changeoccurs in the plate widthwise direction in the rolled material 1.Between the static pressure bearing (two-pocket) 9 and the finish wiperroll 8, the air spring 12 acts, and the static pressure (two-pocket) 9supports the finish wiper roll 8, but the finish wiper roll deflects andthe plate thickness of the end of the rolled material 1 decreases. Thatis, an edge drop (a sharp decrease in plate thickness at the body crownand the plate thickness edge) occurs.

A countermeasure to the edge drop phenomenon that occurs in this way isdifficult, but it is desirable that the roll wiper can cope with thebody crown which is a moderate plate thickness variation.

In the air bearing, the roll is floated by the air pressure, and as theroll pressing force increases, this floating amount decreases. That is,it has the spring property that the floating amount (deflection) changesin response to load. The spring effect of this air pressure is veryimportant for the wiper.

Like the oil film bearing, if this spring constant is large, the rollcannot deflect, and hence the it cannot follow the plate crown.Conversely, if the spring constant is weak, the load capacity becomestoo small, and it follows that the roll and the bearing contact beforefollow-up to the plate crown. The desirable floating amount in the airbearing is about 1/1000 of the roll diameter, for example, if the rolldiameter is 30 mm, the desirable floating amount is 30 μm. A springconstant of the degree to follow-up the plate crown within this floatingamount is desirable. By calculations and experiments, it was confirmedthat the spring characteristics of the air bearing are within thedesirable range.

FIG. 10 shows a diagram explaining the wiping state of the rolledmaterial having the plate crown. We explain the follow-up properties tothe plate crown of the above-mentioned roll wiper of air bearing type.As shown in FIG. 10, at the small plate width edge of plate thickness,the finish wiper roll 8 deflects like the curve 8 a due to the airspring 12 of the static pressure bearing 9 which is the rear airbearing. And, the deflected finish wiper roll 8 comes into contact withthe edge of the rolled material 1. However, the pressing force of thispart becomes lower than the central part. Therefore, it follows that theresidual oil film thickness h2 increases as much as the decrease of theload.

Next, FIG. 11 shows a relation diagram of the follow-up properties tothe body crown of the plate at the roll wiper of air bearing type. Here,the relation between the roll diameter (mm) and the roll deflection (μm)is shown by calculating on the assumption that the roll deflectsaccording to the same quadratic curve as the body crown. In thiscalculation, we calculate assuming that the plate width is 1000 mm andit is tolerated that the residual oil film thickness at the plate widthedge increases by 20% from the central part. That is, we calculated tosee how much plate crown it can respond assuming that the pressing forcedecreases by 20%. Since the calculated value is the deflection of oneroll, the corresponding plate crown is twice the value of FIG. 11.

According to FIG. 11, up to the roll diameter of about 50 mm, the rolldeflection is 15.85 μm˜14.85 μm, it gradually decreases but it is almostthe same. And, as the roll diameter exceeds 50 mm, the roll deflectionsuddenly decreases; when the roll diameter is about 150 mm, itsdeflection amount is very small or 0.58 μm. After all, it is understoodthat as the roll diameter exceeds 50 mm, the roll deflection decreasessuddenly and the ability to respond to the plate crown decreases.Incidentally, even though the roll diameter is 60 mm, the ability torespond to the plate crown slightly decreases, it is within the usablerange.

The above-mentioned study is one in which the load range of the airbearing is identical with the plate width; for example, in the casewhere the present invention is applied to the reverse rolling facility,the plate thickness in the initial pass is large and the plate crown isinevitably large. In this case, since it is not the final pass, a slightdecrease in wiping ability is permissible; but it is possible to let itfollow up the large plate crown by making the load range of the airbearing smaller than the plate width and thereby increasing the rolldeflection.

Slipping of the wiper roll at the time of acceleration and decelerationis conceivable as another factor to determine the wiper roll diameterand we paid our attention to this factor in this example. As the rollslips or the roll velocity decreases below the velocity of the rolledmaterial, the scratching of the rolled material by dust and foreignmatter contained in lubricant occurs. And, scratches occur at the partwhere the roll comes into direct contact with the rolled material, withthe result that the surface quality of the rolled material is impaired.

The friction coefficient f of the roll surface is proportional to theviscosity ν of lubricant, and it is represented by the equation (4)below, where ν: lubricant viscosity (cSt). (This relationship has beeconfirmed by computer simulation.)

f=7·10⁻⁴·ν  (4)

For instance, the friction coefficient is 0.007 at a viscosity of 10cSt. By using this friction coefficient, the critical roll radius R1tthat permits slip to occur at the time of acceleration or decelerationis represented by the equation (5) below.

R 1 t={120·f.P.g/(π·γ·α)}0.5  (5)

where g: acceleration of gravity (9.8 m/sec²), γ: specific weight ofroll (kgf/mm²), α: acceleration or deceleration (m/min/sec).

By using this equation (5), the critical roll diameter was calculatedfor acceleration or deceleration α 60 m/min/sec, pressing force P 0.1kgf/mm (♦ mark), 0.3 kgf/mm (♦ mark), 0.5 kgf/mm (Δ mark), and 1.0kgf/mm (x mark), which are ordinary operating conditions, and theresults are shown in FIG. 12. FIG. 12 shows the critical roll radius atthe time of acceleration and deceleration and shows the relation betweenviscosity (cSt) and the roll radius (mm). By this, for example, it isunderstood that it is necessary to keep the roll radius below 37.3 mm(74.6 mm in diameter) if the lubricant viscosity is 5˜10 cSt and thepressing force is 0.5 kgf/mm (Δ mark).

If the two factors mentioned above are taken into account, it isunderstood that the roll diameter is as small as possible, belowapproximately 60 mm.

And, the limit at the smaller diameter side is considered thatpractically about φ 20 mm is a limit due to the increase in rollrotation in proportion to the smaller diameter and the increase inmachining precision of the static pressure bearing. In other words, thelimit of the smaller diameter side is considered to be about φ 20 mm inconsideration of the increase in roll rotation and the increase inmachining precision of the static pressure bearing.

As mentioned above, increasing the supply air pressure increases thepressing force, and as this pressing force increases, the wiping effectincreases and it is convenient. In the following, we explain the factorthat impedes this.

Here, the relation between the load applied to the wiper roll and thedeflection of the wiper roll is shown in FIG. 5. Since the plate width bgreatly varies depending on operating conditions, in normal operation,as FIG. 5(1) shows, the wiper roll outside the plate width receivesbending force from the static pressure bearing 9 and greatly deflects asthe curve 8 a, by this, the rolled plate 1 is pressed down stronger thanthe center in the vicinity of its edge, and so-called edge elongationand shape defect occur.

This shape defect becomes larger as the roll diameter is smaller. Inorder to prevent this, as shown in FIG. 5(2), if the supply of air ofthe static pressure beating 9 is shut down in the region outside of theplate width b in the plate width direction, the air spring 12 in thatregion does not occur, as 8 b in FIG. 5(2), bending force does not occurin the wiper roll. Therefore, the plate shape is not impaired. As theresult, it is possible to make larger than pressing force. By adjustingthe supply region of air in the plate width direction, it is possible toadjust the roll deflection.

In order to make it possible to correspond finely to the plate width, itis necessary to make the pitch c smaller which is the interval of airsupply holes 23 a in the roll axis direction (widthwise direction of therolled material 1). However, in order to avoid vibrations (pneumatichammer) by air pressure in the air bearing, it is necessary to makesmaller the air pocket; therefore, this pitch c becomes as small asabout 10 mm, and adjustment corresponding to the approximate plate widthbecomes possible, as mentioned above.

According to experiments, with a roll wiper diameter of φ 25 mm and anair supply pressure of 6.5 kgf/cm², excessive pressing down at the platewidth edge does not occur, and good wiping effects were obtained.

As the above-mentioned result, it was confirmed that the roll wiper ofair bearing type of the present invention has the wiping ability equalto or better than the conventional tubular wiper at both high-speedoperation and low-speed operation.

Next, regarding the wiping effect of the rough wiping roll, we explainwith reference to FIG. 2. On the rolled material surface, a large amountof rolling lubricant sticks at the exit of the rolling mill, and this isroughly wiped by the rough wiping roll 6 and then finish wiping isaccomplished by the finish wiper roll 8 of air bearing type.

Therefore, the rough wiping roll 6 is sufficient for the wiper structureof ordinary two-high pinch roll type.

The residual oil film thickness after rough wiping, that is, thisbecomes the oil film thickness h1 at the entrance of the roll wiper ofair bearing type for finishing. For this oil film thickness h1, thedesired pressing force P is added by the rough wiping roll 6.

FIG. 8 shows the result of calculations of the pressing force Pnecessary to obtain the final residual oil film thickness h2. This FIG.8 shows the relation between the oil film thickness (μm) at the entranceand the pressing force (kgf/mm) required, assuming that the oil filmthickness at the exit is 0.5 μm, the wiper roll diameter is φ 25 mm, theviscosity is 10 cSt, and the rolled material advancing speed is 300m/min.

It follows from this that the smaller the oil film thickness hi afterrough wiping, the smaller the pressing force required. That is, thepressing force required to obtain the final oil film thickness 0.5 μm,with h1 being 1000 μm and 10 μm, may be about 15% (←0.46/0.4=1.15)smaller. That is, since the residual oil film thickness h2 is inverselyproportional to the pressing force P, the residual oil film thicknessbecomes about 15% less if the pressing force is the same.

If the oil film thickness after rough wiping is larger than 100 μm,there is almost no effect of its rough wiping; therefore, in the casewhere good wiping is not required, it is not always necessary to installthe rough wiping roll. However, since rolling lubricant sticking at theexit of the rolling mill is supplied in large amounts to the strip wiperand is accumulated gradually, installing it is essential in the casewhere good wiping is required. And, the thinner the oil film at theentrance, the less the residual oil film (since the pressing forcenecessary to obtain the residual oil film greatly reduces, it ispossible to greatly reduce the residual oil film if the wiper pressingforce in the later stage is the same as that in the preceding state);therefore, if finish rolls are placed tandem, a good wiping effect canbe obtained.

The air supply hole of the air bearing is throttled (orifice throttle)by the small diameter d, as shown in FIG. 4, in order to increase therigidity as the air spring of the bearing, its diameter d is as small asφ 0.5-0.7 mm, and is clogged easily with dust and foreign matters. Andthe entrance of water into air becomes the sticking of water to theplate surface, and becomes the occurrence of rust and surface qualitydefects in the later process, and hence is not desirable. Therefore, itis desirable that air to be supplied to the air bearing should be dryair containing almost no moisture which has passed through a finefilter. Moreover, even with such consideration, it is impossible toavoid the occurrence of clogging in this supply hole in operation oflong time.

So, the washing apparatus of the air supply hole (orifice part) on-lineis necessary. This washing is insufficient in washing effect with a gaslike air having a small mass, and washing with the same liquid asrolling lubricant having a high density is effective (if the oil usedfor this washing is the same as the rolling lubricant, there is noproblem even though they are mixed together in the lower part of therolling mill).

EXAMPLE

We explain below the example of the present invention with reference tothe drawings. FIG. 1 shows, as one example of the present invention, asix-high cold rolling mill incorporated with wiper rolls of air bearingtype.

The rolling facility of FIG. 1 is made up of an unwinder 2 to unwind thestrip 1, a 6-high cold rolling mill 3 to roll the strip 1, a strip wiper4 to remove liquid (such as lubricant) from the surface of the strip 1,and a winder 5 to wind up the rolled strip 1.

The 6-high cold rolling mill 3 is made up of a pair of upper and lowerworking rolls 30, a pair of upper and lower intermediate rolls 31 tosupport the working rolls 30, and a pair of upper and lower back-uprolls 32 to support the intermediate rolls 31. It is also provided withrolling lubricant supply means to supply rolling lubricant 10 to the gapbetween the working rolls 30 and the strip 1. In this example, theserolling lubricant supply means are installed at the entrance and exit ofthe 6-high cold rolling mill 3. In other words, the lubricant header 21is installed at the entrance of the 6-high cold rolling mill 3 and thelubricant header 22 is installed t the exit of the 6-high cold rollingmill 3, and they are installed such that they can supply lubricantindependently of each other.

The strip 1 which has been unwound from the unwinder 2 is rolled duringits passage through the 6-high rolling mill 3. Here, the rollinglubricant 10 is supplied from the lubricant header 21 at the entrance ofthe 6-high cold rolling mill 3. Alternatively, the rolling lubricant 10is supplied from both the lubricant header 21 at the entrance of the6-high cold rolling mill 3 and the lubricant header 22 at the exit ofthe 6-high cold rolling mill 3. Subsequently, the rolled strip 1 reachesthe strip wiper 4 installed at the exit of the 6-high cold rolling mill3. Here, the rolling lubricant 10 sticking to the surface of the strip 1is removed, and the strip 1 is wound up by the winder 5.

In this example, two sets of the strip wiper unit 4 are installed. Thefirst strip wiper is installed at the entrance of the strip wiper unit 4and the second strip wiper is installed at the exit of the strip wiperunit 4. The rolling lubricant 10 sticking to the surface of the strip 1can be removed mostly by the first strip wiper at the entrance. And, therolling lubricant 10 (reduced to some extent) sticking to the surface ofthe strip 1 can be removed by second strip wiper at the exit, and thusit is possible to reduce further the rolling lubricant 10 sticking tothe surface of the strip 1.

As the first strip wiper installed at the entrance of the strip wiperunit 4 in this example, a pair of rough wiping rolls 6 are installedover and under the strip. And, as the first strip wiper installed at theexit of the strip wiper unit 4 in this example, a pair of finish wiperrolls 8 are installed over and under the strip.

FIG. 2 shows the construction of the strip wiper unit 4. The strip 1advances at a velocity of v in the strip wiper unit 4. For the rollinglubricant 10 sticking to the surface of this strip 1, the strip isroughly wiped by pressing the strip to the paired upper and lower roughwiping rolls 6 which are the first strip wiper. In other words, beforethe strip 1 passes through the rough wiping roll 6, the thickness (oilfilm thickness) of one side of the rolling lubricant oil 10 sticking tothe surface of the strip 1 is h0. And, much of the rolling lubricant 10on the surface of the strip 1 is removed by the rough wiping roll 6, andthe thickness (oil film thickness) of one side of the rolling lubricantoil 10 becomes h1. That is, it is possible to reduce the oil filmthickness from h0 to h1.

Subsequently, the rolling lubricant 10 which sticks to the surface ofthe strip 1 and whose oil film thickness is h1 undergoes finish wipingby pressing the strip against the paired upper and lower finish wiperrolls which are the second strip wiper. In other words, before the strip1 passes through the finish wiper roll 8, the thickness (oil filmthickness) of one side of the rolling lubricant oil 10 sticking to thesurface of the strip 1 is h1. And, the rolling lubricant 10 remaining onthe surface of the strip 1 is efficiently removed by the finish wiperroll 8, and the thickness (oil film thickness) of one side of therolling lubricant oil 10 becomes h2. That is, it is possible reduce theoil film thickness from h1 to h2. Incidentally, this finish wiper roll 8is supported by the air static pressure bearing 9 of two-pocket type, sothat it can reduce the residual oil film.

Since the wiping means of the rough wiping roll 6 and the wiping meansof the finish wiper roll 8 are arranged sequentially from the entranceas mentioned above, it is possible to roughly remove oil film by therough wiping roll 6 and adequately remove oil film by the finish wiperroll 8. Moreover, it is possible to obtain the superior wiping abilityby removing oil film with good precision by supporting the finish wiperroll 8 by the fluid bearing.

FIG. 3 shows a sectional view in the axial direction of the finish wiperroll. The finish wiper rolls 8 are arranged as if they hold the strip 1between them. The thrust blocks 25 are installed to prevent the finishwiper rolls 8 from dislocating in the axial direction. The staticpressure bearings 9 having the gap 23 d are arranged so as to supportthe finish wiper roll 8, and the first air supply holes 23 a are formedin the roll side of the static pressure bearing 9. Air is supplied tothis first air supply hole 23 a and the wiper roll 8 is rotatably heldby static pressure, with the gap 23 d between them. This first airsupply hole 23 a is formed approximately in the roll radial direction,pointing toward the roll axial center, with two formed in the rollcircumferential direction and a plurality formed in the roll axialdirection.

In this example, air is supplied to the air distributing hole 23 oncebefore air is supplied to the first air supply hole 23 a. This airdistributing hole 23 forms one air chamber penetrating in the roll axialdirection. In other words, air is introduced into the gap 23 d from theair distributing hole 23 through the air supply holes 23 a.

And, the air distributing hole 23 is provided with the adjusting rod 13on both sides in the roll axial direction. This adjusting rod 13 movesin the roll axial direction in the air distributing hole 23 and canadjust the air supply region in the roll axial direction (in the stripwidthwise direction). As the mechanism to move this adjusting rod 13 inthe roll axial direction, the hydraulic cylinders 24 are installedrespectively in this example.

To the above-mentioned air distributing hole 23, air is supplied throughthe second air supply hole 23 c from the outside. This second air supplyhole 23 c is outside the static pressure bearing and is installedapproximately in the roll radial direction. And, the second air supplyhole 23 c is installed in a plural number in the roll axial direction.In this example, the size of the second air supply hole 23 c is smallerthan the size of the first air supply hole 23 a, so as to facilitate airsupply. And, the interval of arrangement of the second air supply holes23 c is larger than the interval of arrangement of the first air supplyholes 23 a, so as to facilitate air supply. It is desirable to makesmall the first air supply hole 23 a at the roll side and to make smalltheir arrangement intervals. By making small the first air supply hole23 a at the roll side, it is possible to stabilize the roll support, andby making small their arrangement intervals, it is possible to make fineadjustment for the air region.

As mentioned above, high-pressure air is supplied through a plurality ofair supply holes 23 c from the backside of the static pressure bearing9. This air is supplied further to the finish wiper roll 8 from theintermediate air distributing hole 23 through orifices (diameter d)arranged with a small pitch c so as to generate the floating force. Thisfloating force becomes the pressing force P of the wiper.

In this air distributing hole 23 is installed the adjusting rod 13changeable in the widthwise direction in both sides of the axialdirection, so that it is possible to adjust the supply width of air tothe orifices. By this, it is possible to adjust in response to the platewidth b the range to which the floating force of air of the staticpressure bearing of the wiper roll applies.

Adjusting the range to which the floating force of the finish wiper roll8 is applied corresponds to changing its width in which the finish wiperroll 8 is held by the air spring as shown in FIG. 5. FIG. 5(1) is one inwhich the above-mentioned adjustment in the widthwise direction is notperformed and the finish wiper roll 8 is floated and supported for theentire width; the finish wiper roll 8 is not uniform in deflection inthe widthwise direction, the pressing force at the plate width edge islarge and the strip is excessively pressed accordingly, and edgeelongation and shape defect occur. As the result, it follows that it isimpossible to raise the wiper pressing force. On the other hand, asshown in FIG. 5(2), if the range of the air floating force is made tocoincide approximately with the plate width b, the deflection of thefinish wiper roll 8 becomes uniform in the axial direction, theoverpressing of the plate width 10 end does not occur, it is possible togreatly increase the wiper pressing force P, as the result, the wipingeffect greatly improves.

Also, FIG. 3 shows the cleaning unit to prevent the clogging of theorifice (the first air supply hole 23 a) of the static pressure bearing9. During operation in a certain period, air is supplied to the secondsupply hole 23 c from the air supply unit 11 through the switching valve15. And, after operation for a certain period, for example, the supplyof air from the air supply unit 11 is suspended by the switching valve15 and the cleaning oil is supplied from the cleaning oil supply unit14. In this way, cleaning oil is introduced into the first air supplyhole 23 a through the second air supply hole 23 c and the airdistributing hole 23, and it is possible to remove dust and foreignmatters clogging the orifice (the first air supply hole 23 a). Thereducing valve 16 is installed so that it is possible to adjust thesupply pressure of the cleaning oil according to the load bearingcapacity of the static pressure bearing of air. Incidentally, atresumption of operation, the supply of cleaning oil from the cleaningoil supply unit 14 is suspended by the switching valve 15 and air issupplied from the air supply unit 11; in this way, air is introducedinto the first air supply hole 23 a through the second air supply hole23 c and the air distributing hole 23, and the roll support becomespossible.

FIG. 9 is another example of the present invention, in which the 6-highcold rolling mill of FIG. 1 has been replaced by a 20-high Sendzimircold rolling mill. Likewise, it is apparent that the present inventioncan be applied to multiple cluster rolling mills other than 20-highones.

FIG. 10 is a diagram explaining the state in which the finish wiper roll8 is deflected by the plate crown present in the strip. For the wiperroll 8 to deflect following the plate crown, it is necessary that thebending rigidity of the wiper roll is small and it is understood thatthe wiper roll of small diameter is advantageous. However, the resultsof calculations of FIG. 11 are affected also by the spring constant ofthe air bearing, in the overall effect with the bending rigidity of theroll, there is no significant difference in ability to follow the platecrown in the case of roll diameter smaller than φ 50 mm.

FIG. 7 is an example in which the roll wipers of air bearing type arearranged tandem in order to increase the wiping effect, by arranginglike this, a further superior wiping effect is obtained.

The wiping unit of the present invention, at high-speed rollingexceeding 700 m/min which was incapable with the conventional roll wiperor tube wiper, it is possible to obtain the wiping ability equal to orbetter than the tube wiper at low speeds, and it contributes to theimprovement of productivity of the cold rolling facility and theimprovement of surface quality of the strip, and its effect is verylarge.

According to the present invention, the effect produced is that it ispossible to provide the strip wiper unit superior in wiping ability toremove liquid from the strip surface, the method of wiping the strip,and the rolling facility and the rolling method.

What is claimed is:
 1. A strip wiper device to remove liquid from astrip surface which comprises: a wiper roll to remove liquid from thestrip surface; a fluid bearing to support the wiper roll, with the fluidbearing having at least two fluid passages in the circumferentialdirection of the roll; and an adjusting means to make adjustable theload bearing width in the strip width direction of said fluid bearing.2. A strip wiper device as defined in claim 1, wherein the air supplypressure of said fluid bearing is greater than 5 kgf/cm².
 3. A stripwiper device as defined in claim 1, which further comprises a supplyunit to supply cleaning oil to the fluid passage of said bearing.
 4. Astrip wiper device as defined in claim 1, wherein respective ones ofsaid wiper rolls supported by respective ones of said static pressurebearings are arranged in use respectively at an upper side and a lowerside of a strip with said strip surface.
 5. A strip wiper deviceaccording to claim 2, which further comprises a supply unit to supplycleaning oil to the fluid passage of said static pressure bearing.
 6. Astrip wiper device according to claim 2, wherein the wipe rollssupported by said static pressure bearing are arranged respectively atthe upper side and lower side of the strip.
 7. A strip wiper deviceaccording to claim 3, wherein the wipe rolls supported by said staticpressure bearing are arranged respectively at the upper side and lowerside of the strip.
 8. A strip wiper device to remove liquid from a stripsurface which comprises a first strip wiper and a second strip wiperwhich are arranged sequentially in the direction of strip advance, thesecond strip wiper being made up of: a wiper roll; a fluid bearing tosupport the wiper roll, with the fluid bearing having at least two fluidpassages in the circumferential direction of the roll; and an adjustingmeans to make adjustable the load bearing width in the strip widthdirection of said fluid bearing.
 9. A strip wiper device as defined inclaim 8, wherein the diameter of the wiper roll of said second stripwiper is in the range of 20-60 mm.
 10. A strip wiper device according toclaim 8, wherein the diameter of the wiper roll of said second stripwiper is in the range of 20˜60 mm.
 11. A strip wiper device according toclaim 8, wherein the air supply pressure of said fluid bearing isgreater than 5 kgf/cm².
 12. A strip wiper device according to claim 9,wherein the air supply pressure of said fluid bearing is greater than 5kgf/cm².
 13. A strip wiper device according to claim 8, which furthercomprises a supply unit to supply cleaning oil to the fluid passage ofsaid static pressure bearing.
 14. A strip wiper device according toclaim 9, which further comprises a supply unit to supply cleaning oil tothe fluid passage of said static pressure bearing.
 15. A strip wiperdevice according to claim 8, wherein the wipe rolls supported by saidstatic pressure bearing are arranged respectively at the upper side andlower side of the strip.
 16. A strip wiper device according to claim 9,wherein the wipe rolls supported by said static pressure bearing arearranged respectively at the upper side and lower side of the strip. 17.A strip wiper device to remove liquid from a strip surface in coldrolling which comprises a first strip wiper for rough wiping and asecond strip wiper for finishing which are arranged sequentially in thedirection of strip advance, the second strip wiper being made up of: awiper roll; a fluid bearing to support the wiper roll by pneumaticpressure, with the fluid bearing having at least two fluid passages forapplying pneumatic pressure to the wiper roll at respective locationsspaced in the circumferential direction of the roll, such that the wiperroll is supported by pneumatic pressure in two directions from the twofluid passages; and an adjusting means to make adjustable the loadbearing width in the strip width direction of said fluid bearing.
 18. Astrip wiper device according to claim 17, wherein the diameter of thewiper roll of said second strip wiper is in the range of 20˜60 mm.
 19. Astrip wiper device according to claim 17, wherein the air supplypressure of said fluid bearing is greater than 5 kgf/cm².
 20. A stripwiper device according to claim 17, which further comprises a supplyunit to supply cleaning oil to the fluid passage of said static pressurebearing.
 21. A strip wiper device according to claim 17, wherein thewipe rolls supported by said static pressure bearing are arrangedrespectively at the upper side and lower side of the strip.
 22. A stripwiper device to remove liquid from a strip surface which comprises afirst strip wiper and a second strip wiper which are arrangedsequentially in the direction of strip advance, the first and secondstrip wipers each being made up of a wiper roll and a fluid bearing tosupport the wiper roll, with the fluid bearing having at least two fluidpassages in the circumferential direction of the roll, and an adjustingmeans to make adjustable the load bearing width in the strip widthdirection of said fluid bearing.
 23. A strip wiper device to removeliquid from a strip surface which comprises a first strip wiper and asecond strip wiper which are arranged sequentially in the direction ofstrip advance, the second strip wiper being made up of a wiper roll anda fluid bearing to support the wiper roll; and an adjusting means tomake adjustable the load bearing width in the strip width direction ofsaid fluid bearing.
 24. A method of strip wiping to remove liquid from astrip surface which is characterized in that wiper rolls supported byfluid bearings are arranged above and below the strip surface, with therespective fluid bearings having at least two fluid passages in thecircumferential direction of the roll, the fluid passages being suppliedwith a fluid so that the wiper roll is borne by the fluid and is pressedagainst the strip; and wherein the load bearing width in a strip widthdirection of said fluid bearing is adjusted according to rollingconditions.
 25. A method of strip wiping to remove liquid from a stripsurface of a strip which is characterized in that a wiper roll for roughwiping removes liquid from the strip surface and wiper rolls supportedby fluid bearings are arranged above and below the strip at thedownstream side, with the fluid bearings having at least two fluidpassages in the circumferential direction of the roll, the fluidpassages being supplied with a fluid so that the wiper roll is borne bythe fluid and is pressed against the strip; and wherein the load bearingwidth in a strip width direction of said fluid bearing is adjustedaccording to rolling conditions.
 26. A rolling facility which comprisesa rolling mill and a strip wiper device to remove liquid from the stripsurface at the exit of the rolling mill, said strip wiper device beingmade up of a wiper roll to remove liquid from the strip surface, a fluidbearing to support the wiper roll, with the fluid bearing having atleast two fluid passages in the circumferential direction of the roll;and an adjusting means to make adjustable the load bearing width in thestrip width direction of said fluid bearing.
 27. A rolling facility asdefined claim 26, wherein said rolling mill is one of a 6-high rollingmill provided with a lubricant supply unit to supply lubricant betweenrolls, and a multiple cluster rolling mill (including a 20-highSendzimir rolling mill) provided with a lubricant supply unit.
 28. Arolling method to be applied to a rolling facility made up of a rollingmill and a strip wiper device to remove liquid from a strip surface atthe exit of the rolling mill, said method being characterized in thatwiper rolls supported by fluid bearings are arranged over and under thestrip, the fluid bearings having at least two fluid passages in acircumferential direction of the roll and the passages are supplied witha fluid so that the wiper roll is borne by the fluid, and the wiper rollis pressed against the strip so that liquid is removed from the stripsurface while rolling is carried out; and wherein the load bearing widthin a strip width direction of said fluid bearing is adjusted accordingto rolling conditions.
 29. A rolling method to be applied to a rollingfacility made up of a rolling mill and a strip wiper device to removeliquid from a strip surface at the exit of the rolling mill, said methodbeing characterized in that a wiper roll for rough wiping removes mostliquid from the strip surface, wiper rolls supported by fluid bearingsare arranged over and under the strip, the fluid bearings having atleast two fluid passages in a circumferential direction of the roll andthe passages are supplied with a fluid so that the wiper roll issupported in two directions by pneumatic pressure, and the wiper roll ispressed against the strip so that liquid remaining unremoved by thewiper for rough wiping is removed from the strip surface while rollingis carried out; and wherein the load bearing width in a strip widthdirection of said fluid bearing is adjusted according to rollingconditions.
 30. A strip wiper device which comprises: a wiper roll toremove liquid from a strip surface; a fluid bearing to support the wiperroll, said fluid bearing having at least two fluid jet nozzles towardthe wiper roll in the circumferential direction of the roll; and anadjusting means to make adjustable the load bearing width in the stripwidth direction of said fluid bearing.
 31. A strip wiper device whichcomprises: a wiper roll to remove liquid from a strip surface; a fluidbearing to support the wiper roll, said fluid bearing having at leastone each fluid jet nozzle at the entrance and exit from the wiper rollaxis center; and an adjusting means to make adjustable the load bearingwidth in the strip width direction of said fluid bearing.
 32. A stripwiper device which comprises: a wiper roll to remove liquid from a stripsurface; a fluid bearing to support the wiper roll, said fluid bearinghaving at least two fluid jet nozzles toward the wiper roll in thecircumferential direction of the roll, said jet nozzles being arrangedsuch that their jet direction is toward the wiper axis center; and anadjusting means to make adjustable the load bearing width in the stripwidth direction of said fluid bearing.
 33. A method of making stripmaterial comprising: rolling a strip of material in a rolling mill toreduce the thickness of the strip while applying a lubricant to saidstrip, removing a substantial portion of said lubricant from said stripat a position downstream of the rolling mill in a strip wiper assembly,and coiling said strip on a coiler disposed downstream of the stripwiper assembly, said removing of said lubricant step including pressingrespective wiper rolls against upper and lower sides of said strip withsaid wiper rolls supported by fluid bearing and wherein the pressure ofthe fluid bearings is adjusted across the strip width as a function ofthe rolling conditions in the rolling mill.
 34. A method according toclaim 33, wherein each of the fluid bearings include a plurality ofcircumferentially spaced fluid openings to the respective wiper rolls.35. A method according to claim 33, wherein said pressure bearings arepneumatic bearings operable with air pressure greater than 5 kfg/cm².36. A method according to claim 33, wherein the diameter of said wiperrolls is between 20 and 60 mms.
 37. A method according to claim 33,further comprising periodic cleaning of fluid openings of said fluidbearings using pressurized flow of said lubricant.
 38. A methodaccording to claim 35, comprising periodic cleaning of fluid openings ofsaid fluid bearings using pressurized flow of said lubricant.